Ran into trouble using proxies that were generated without the same number of audio channels as the original source. Without matching audio track assigns PPro will not allow it to be a workable proxy.

Worked out a number of ways to accommodate this and a series of consequent challenges, but in retrospect, would it no make more sense for PPro's proxy logic to allow it to ignore audio altogether. Sound is not generally the playback bottleneck necessitating proxies, so would it not make more sense, in Proxy mode, to use picture-only from the Proxy, sound only from the Original?

I can imagine, for technical reason, this is not possible: perhaps playing sound from the original media requires the same throughput as playing sound + picture. But who knows.

Since yesterday got some interesting progress. Switching over to ffmpeg (instead of AME) for proxies I was able to generate an MP4 file (wrapper) with H264 video and AAC audio, all tracks mapped properly from source. It works perfectly as a PPro Proxy.

The benefits of the ffmpeg/MP4 approach are pretty dramatic

Starting with an original UHD "4k" file with 4 channels of audio at 27gb

Codec

File Size

Savings

Original File: MXF wrapper

VIdeo: H.264

Audio: PCM (4 channels)

27gb

original file

Cineform at 1270x720 Quality 5 (highest)

5.2gb

5x

Cineform at 1270x720 Quality 1 (lowest)

1.9gb

14x

Cineform at 640x360 Quality 1 (lowest) (terrible)

887mb

31x

ffmpeg-generated MP4 file

Video: H.264

Audio: AAC (4 channels)

373mb

73x !!

The quality of the ffmpeg-generated MP4 is excellent, and can be dialed up or down depending on file size / quality tradeoff

The channel mapping is automatic, so 2-channel sources and 4-channel sources map appropriate to the final.

The down-side of using FFMPEG is the effort involved in leaving the Adobe ecosystem / working in Command Line.

The Proxies don't connect by themselves, so you're either manually doing each on individually or running some ExtendScript to connect in batch.But you also have more custom control over naming conventions and target folder than you do with AME.

So the good news is that it is possible create a Premiere-Compatible Proxy file with excellent quality at small file sizes using H.264 compression and more than 2 channels of sound.

I think you've got the wrong viewpoint here. The point of proxies is to make editing easier. In the early days of NLE's, hard drives were the limiting factor, so smaller files made sense. Today, the CPU is the limiting factor, where the small file size (compression) is actually the problem.

I think the best option is to just use the included Cineform presets. Hard drives are cheap.